This invention relates to a mounting disk for use in mounting a floor polishing pad on a motorized floor polishing machine. The invention also relates to a method of forming the mounting disk through a molding process which provides an integral mounting disk formed from disparate plastic starting materials to provide an improved composite product having improved strength properties as well as enhanced resiliency.
Industrial floor polishers have been in use for many years in the industrial setting for scrubbing or polishing large commercial areas. These apparatuses are typically electric powered in smaller applications but may also be gas powered, and typically by liquid propane, for use in settings where greater horsepower is desired.
Floor polishers typically include a driven shaft which receives an attachment for brushing or polishing floor surfaces. The attachment may take the form of a brush having heavy duty bristles as is illustrated, for example, in U.S. Pat. Nos. 3,172,142 and 3,183,542. As discussed in these patents, a polishing pad is applied directly to the bristles or may be securely held in position by a pad holder which includes an outer flange providing a lip which exerts force on the polishing pad to maintain the frictional engagement between the pad and the bristles. Alternatively, and as shown in U.S. Pat. No. 4,307,480, the positioning of the polishing pad may be maintained by a supporting structure in which the pad is sandwiched between two members with the upper member providing the backup for the polishing pad; a function which would alternatively be provided by the bristles on the brush as described above.
A common shortcoming of the devices for mounting the polishing pad is the inability of the mounting disk to provide for a sufficient degree of flexure in the pad so that the polishing pad maintains contact with the floor on encountering uneven surfaces such as a door threshold or the like. The apparatuses disclosed in the U.S. Pat. Nos. 3,172,142 and 3,183,542 rely on the flexiblity of the bristles which must be compressed in order to provide any flexure for the pad upon encountering a protuberance on the surface of the floor. Since these bristles typically have a high level of stiffness, the pad will generally be subjected to extreme wear and rapid deterioration when a threshold or the like is contacted with the polishing pad.
Efforts to provide for flexibility at the peripheral areas of a polishing pad are represented by U.S. Pat. No. 3,395,417, for example, which describes a multi-layered structure in which a pad made of soft urethane foam is joined to a plate which is stiffer than the pad. As noted in U.S. Pat. No. 4,322,866, however, difficulties have been encountered with this structure due to the glue interfaces between the foam and the surface of the disk in the multi-layered constructions. This patent also notes that a problem is encountered in the use of soft polystyrene composite devices because of a tendency for the disk to wobble in use. To this end, the latter patent advocates the use of an elastomeric disk with a thick central zone and a relatively thin peripheral zone. The annular portion is formed of elastomeric material, and particularly rubber having a specified durometer hardness. An annular groove is also provided on the periphery of the attachment in an effort to provide the desired flexibility in the peripheral areas. The provision of the groove however significantly reduces the strength of the attachment in this critical region particularly since the periphery will absorb all of the resulting stresses as portions of the polisher engage an uneven surface during polishing.
It is therefore an object of the present invention to provide a mounting disk for mounting a polishing pad on a floor polisher of the type described which provides the desired resiliency, but which also possesses significant strength properties in order to avoid rapid deterioration of the mounting disk. It is also an object of the invention to provide a mounting disk having an annular, unitary lip for maintaining the pad in engagement against a backing member.
It is also an object of the invention to provide a method of fabricating a floor polisher mounting disk which provides the desired resilient properties through the composite structure disclosed hereinbelow but which is substantially unitary to provide a disk having improved strength properties as well.